Where liquid level measurement, gas or liquid flow measurement and the like are being conducted in the presence of an explosive or other hazardous environment, electrically or electronically operated measuring equipment is typically avoided because of the hazards that are prevalent when electrical apparatus is employed. For the most part such measuring equipment is of mechanical nature or of electromagnetic nature such that the measurement signals provided thereby may be safely converted into electrical signals and processed at a remote location.
In cases where electrical activity is located in a hazardous environment such as when explosive vapors may be present, it is typical for the electronic equipment and circuitry to be isolated by means of sealed closures, metal conduits and the like. Further, to ensure against the possibility of electrical potential transfer along the electrical circuitry, the hard metal conduits which isolate the circuitry from the potentially explosive environment are provided with internal safety barriers. Such installations are very expensive and thus detract from the commercial feasibility of the activity to the extent that mechanical measurement devices are preferred if at all possible.
Since many flow measurement devices, liquid level sensors, etc. are of mechanical nature, they are subject to a number of anomalies that are inherent in mechanical devices. Mechanical flow and level measurement devices are subject to some degree of inaccuracy because integrated moving parts tend to become worn and mechanical accuracy is therefore subject to deterioration through use and time. Further, mechanical measurement devices are subject to becoming fouled by dirt and by the products that are being measured and tend to become inaccurate as the result of fouling. It is desirable, therefore, to provide a measurement system capable of measuring the flow of gases and liquids and also being capable of measuring the liquid level within vessels. It is also desirable to provide a measurement system that is capable of extreme accuracy and a high degree of resolution, is inherently safe and is not subject to inaccuracy due to wear or fouling of the mechanical components thereof.